Severe weather - November 5-6, Midwest/South

[CrazyC83]

It's been a quiet October, but models seem to point to an active time in early November. It's still way too early to tell (nearly a week away), but the SPC has hinted of something, and NWS Grand Rapids has already hinted at such for next Thursday (November 6). Looking at the models, this seems to be one that may cover a large area...

&&

.LONG TERM...(1215 PM EDT WED OCT 30 2008)
(SUNDAY THROUGH THURSDAY)

FAIR AND SEASONABLY MILD WX IS ANTICIPATED THROUGH SUNDAY
AFTERNOON. A FEW SHOWERS WILL ARRIVE SUNDAY NIGHT IN ASSOCIATION
WITH THE WARM FRONT AND MID LEVEL SHORTWAVE.

STRONG WARM AIR ADVECTION WILL DEVELOP FROM MONDAY THROUGH
WEDNESDAY... LEADING TO MUCH ABOVE NORMAL TEMPS. THE WX PATTERN WILL
BECOME QUITE UNSETTLED LATE IN THE WEEK. THE CONTINUED SOUTHERLY
FLOW OFF THE GULF WILL RESULT IN INCREASING MOISTURE IN ADVANCE OF A
STRONG COLD FRONT.

THIS WILL SET THE STAGE FOR DEVELOPMENT OF SHOWERS AND THUNDERSTORMS
THURSDAY. IN FACT... GIVEN THE POTENTIAL STRENGTH OF WIND FIELDS AND
DYNAMICS ASSOCIATED WITH THAT SYSTEM... SEVERE WEATHER IS POSSIBLE
THURSDAY.

http://www.crh.noaa.gov/product.php?sit ... suedby=grr

[CrazyC83]

ZCZC SPCSWOD48 ALL
ACUS48 KWNS 310848
SPC AC 310848

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0348 AM CDT FRI OCT 31 2008

VALID 031200Z - 081200Z

...PREDICTABILITY IS STILL TOO LOW TO CONFIDENTLY DELINEATE A SEVERE
THREAT AREA...

LINGERING SURFACE RIDGING ACROSS THE GULF COAST REGION...IN THE WAKE
OF A DEPARTING SOUTHERN BRANCH TROUGH...STILL APPEARS LIKELY TO
INHIBIT THE POTENTIAL FOR SEVERE STORMS NEXT MONDAY AND TUESDAY
...WHEN MEDIUM RANGE FORECAST GUIDANCE INDICATES SURFACE
CYCLOGENESIS WILL COMMENCE TO THE LEE OF THE ROCKIES IN RESPONSE TO
THE APPROACH OF AN AMPLIFIED POLAR TROUGH. THEREAFTER...A STRONG
SIGNAL EXISTS AMONG THE MODELS CONCERNING INCREASING POTENTIAL FOR A
SIGNIFICANT SEVERE WEATHER EVENT...AS STRONG SURFACE CYCLOGENESIS
PROCEEDS FROM THE CENTRAL PLAINS INTO THE UPPER GREAT LAKES...AND A
SUBSTANTIAL RETURN FLOW OF MOISTURE OFF THE GULF OF MEXICO BECOMES
MORE LIKELY. THE GREATEST RISK APPEARS TO EXIST ACROSS PARTS OF THE
SOUTHEASTERN PLAINS THROUGH THE OZARK PLATEAU AND LOWER/MIDDLE
MISSISSIPPI VALLEYS NEXT WEDNESDAY INTO NEXT THURSDAY. BUT...THIS
IS COINCIDENT WITH RAPIDLY GROWING SPREAD AMONG MREF MEMBERS
CONCERNING THE PROGRESSIVENESS OF THE UPPER TROUGH AND ASSOCIATED
LARGE-SCALE PATTERN EVOLUTION.

..KERR.. 10/31/2008

CLICK TO GET WUUS48 PTSD48 PRODUCT

[vbhoutex]

This is one of the times of year we do see severe weather here in SE TX. But this sounds like it will be North of us.

[Ed Mahmoud]

Tuesday evening- low level jet in excess of 60 knots per Euro



Strong diffluent jet at somewhat of an angle to low level flow...


Might take a little more time to get good moisture return. Euro has slightly weaker looking wind fields, but better moisture return on Wednesday.

[CrazyC83]

The wind patterns suggest tornadoes would be the main threat if it does happen.

[CrazyC83]

SPC now picking up on it, no mention of November 6 yet though:

ZCZC SPCSWOD48 ALL
ACUS48 KWNS 010857
SPC AC 010857

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0357 AM CDT SAT NOV 01 2008

VALID 041200Z - 091200Z

...SEVERE STORMS POSSIBLE ACROSS PARTS OF THE SOUTHERN/EASTERN
PLAINS INTO THE OZARK PLATEAU/LWR MISSOURI VALLEY NEXT WEDNESDAY...

MEDIUM RANGE FORECAST GUIDANCE CONTINUES TO INDICATE THAT FAIRLY
STRONG SURFACE CYCLOGENESIS WILL ACCOMPANY AN AMPLIFIED POLAR TROUGH
TO THE LEE OF THE ROCKIES DURING THE EARLY TO MIDDLE PART OF THE
COMING WORK WEEK. AND...CONFIDENCE IS HIGH THAT A SIGNIFICANT
RETURN FLOW OF MOISTURE OFF THE GULF OF MEXICO WILL FINALLY DEVELOP
BY WEDNESDAY...SUPPORTING INCREASING CONVECTIVE POTENTIAL ACROSS THE
CENTRAL STATES. THE WARM SECTOR MAY NOT BECOME PARTICULARLY BROAD
DUE TO THE CONTINUING PRESENCE OF A SURFACE RIDGE ACROSS THE EASTERN
STATES INTO LATE WEEK. BUT...IT SEEMS PROBABLE THAT AT LEAST A
MODEST OUTBREAK OF SEVERE WEATHER WILL OCCUR IN A CORRIDOR FROM
PARTS OF NORTHEAST TEXAS NORTHWARD INTO IOWA...NEXT WEDNESDAY INTO
WEDNESDAY NIGHT.

CONSIDERABLE SPREAD CONTINUES TO EXIST AMONG THE MODELS AND MREF
MEMBERS CONCERNING THE STORM EVOLUTION...INCLUDING THE TRACK OF THE
PRIMARY SURFACE LOW. IF THE MORE SOUTHERN TRACK OF THE LATEST GFS
COMES TO FRUITION /IN CLOSER PROXIMITY TO THE DEVELOPING RETURN
FLOW/...THEN THE SEVERE POTENTIAL WILL PROBABLY BE SIGNIFICANTLY
GREATER THAN IF THE MORE NORTHERN TRACK OF THE ECMWF VERIFIES.

..KERR.. 11/01/2008

CLICK TO GET WUUS48 PTSD48 PRODUCT

[CrazyC83]

Moisture return potential: Based on models, northern runs mean dewpoints mostly in the high 50s, and southern runs mostly low 60s. Temperatures mostly in the mid to high 60s in the north and low 70s in the south.

Comparable recent fall events and dewpoints:

November 6, 2005 (Evansville) - Temperatures high 60s, dewpoints low 60s
November 12, 2005 (Iowa) - Temperatures high 60s, dewpoints high 50s
November 15, 2005 (Central US) - Temperatures mid-70s, dewpoints mid-60s
November 27, 2005 (Mid-South) - Temperatures low 70s, dewpoints low 60s
November 15, 2006 (Deep South) - Temperatures low 70s, dewpoints low 60s
October 18, 2007 (Midwest) - Temperatures low 80s, dewpoints low 70s

Comparison with the two biggest winter outbreaks this year:

January 7, 2008 (Midwest) - Temperatures mid-60s, dewpoints mid-50s
February 5, 2008 (Mid-South) - Temperatures low 70s, dewpoints mid-60s

[Shockwave]

What do you guys think the chances are of this possible event affecting us here in Middle TN? My opinion is, is that we may be on the northern edge of this event, but it is getting into the Secondary Severe season for us, and am I ready for it.

[CrazyC83]

What do you guys think the chances are of this possible event affecting us here in Middle TN? My opinion is, is that we may be on the northern edge of this event, but it is getting into the Secondary Severe season for us, and am I ready for it.

Middle Tennessee actually appears to be in the southern part of the activity. Your best chance would be Thursday if the low tracks farther south.

NWS Paducah getting nervous - CAPE won't be that high but shear could be impressive and helicity off the charts, so even CAPE values around 1,000 J/kg2 could lead to a major tornado outbreak in the atmosphere the models suggest:

LATEST MODEL RUNS SUGGEST POSSIBLY A SQUALL LINE PASSAGE THEN DRY IN
ITS WAKE WHICH ALSO SUPPORTED NARROWING THE PRECIP WINDOW SOMEWHAT.
12Z SAT GFS FORECAST SOUNDING SHOWING LOW LEVEL JET WED NGT BETWEEN
35 AND 45 KNOTS. ALTHOUGH THE STABILITY PARAMETERS ARE NOT ALL THAT
IMPRESSIVE WITH ML CAPE LESS THAN 500 J/KG2. THE WINDS SUGGEST
SEVERE OR EVEN TOR POTENTIAL. 0-3 BULK SHEAR OF 30-40 KNOTS. THE
HODOGRAPH SHOWS SOME GOOD CURVATURE IN THE LOW LEVELS. 0-3 SRH
SURPASS 300 M2S-2. ALSO WE ARE ENTERING INTO THE HEART OF OUR
SECONDARY SEVERE WEATHER SEASON.

http://www.crh.noaa.gov/product.php?sit ... suedby=PAH

[Shockwave]

Thanks CrazyC83, the newer runs show it even going further north then before. Looks like we may be on the fringe with this activity. I'm so anxious for storms...I seriously thought I heard the NOAA radio go off this morning.

[CrazyC83]

ZCZC SPCSWOD48 ALL
ACUS48 KWNS 020939
SPC AC 020939

DAY 4-8 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0339 AM CST SUN NOV 02 2008

VALID 051200Z - 101200Z

...SEVERE STORMS POSSIBLE ACROSS THE EAST CENTRAL PLAINS INTO THE
MID AND LOWER MISSISSIPPI VALLEY THIS COMING WEDNESDAY/THURSDAY...

THE SPREAD AMONG MEDIUM RANGE FORECAST MODELS AND MREF ENSEMBLE
MEMBERS IS NOW REASONABLY LOW THROUGH THE MIDDLE TO LATTER PORTIONS
OF THE COMING WORK WEEK. STRONG SURFACE CYCLOGENESIS IS PROGGED TO
ACCOMPANY AN AMPLIFIED POLAR TROUGH EAST OF THE ROCKIES INTO THE
MISSISSIPPI VALLEY BY WEDNESDAY/THURSDAY. WHILE IT APPEARS MOST
PROBABLE THAT THE PRIMARY SURFACE LOW WILL TAKE A NORTHERN TRACK
THROUGH THE NORTHERN PLAINS/UPPER MISSISSIPPI VALLEY...GUIDANCE IS
SUGGESTIVE THAT A COLD FRONT/DRY LINE INTERSECTION ACROSS THE
CENTRAL PLAINS WILL PROVIDE THE FOCUS FOR INTENSE CONVECTIVE
DEVELOPMENT AS THE POLAR JET CORE BEGINS TO OVERSPREAD IT WEDNESDAY
AFTERNOON. AND...A SUBSTANTIVE RETURN FLOW OFF THE GULF OF MEXICO
APPEARS LIKELY TO CONTRIBUTE TO SUFFICIENT INSTABILITY FOR A FEW
SUPERCELLS IN THE PRESENCE OF STRONG SHEAR...BEFORE LARGE-SCALE
FORCING SUPPORTS POSSIBLE UPSCALE GROWTH INTO AN EXTENSIVE SQUALL
LINE WEDNESDAY NIGHT. ALTHOUGH THE WARM SECTOR MAY NOT BECOME
PARTICULARLY BROAD...A STRONG/SEVERE SQUALL LINE MAY ADVANCE THROUGH
MUCH OF THE MID AND LOWER MISSISSIPPI VALLEY BY THURSDAY
AFTERNOON...BEFORE ACTIVITY DIMINISHES AS THE CYCLONE OCCLUDES
ACROSS THE UPPER MISSISSIPPI VALLEY.

..KERR.. 11/02/2008

CLICK TO GET WUUS48 PTSD48 PRODUCT

[Dave]

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE LINCOLN IL
528 AM CST SUN NOV 2 2008

ILZ062-063-066>068-071>073-031200-
CLARK-CLAY-CRAWFORD-CUMBERLAND-EFFINGHAM-JASPER-LAWRENCE-RICHLAND-
528 AM CST SUN NOV 2 2008

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF EAST CENTRAL
ILLINOIS AND SOUTHEAST ILLINOIS.

.DAY ONE...TODAY AND TONIGHT

PATCHY DENSE FOR WILL LIMIT VISIBILITIES TO LESS THAN ONE HALF MILE
IN A FEW LOCATIONS THIS MORNING...ESPECIALLY IN LOW LYING AREAS AND
NEAR RIVER VALLEYS. CONDITIONS WILL RAPIDLY IMPROVE BY 900 AM.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY

A STRONG LOW PRESSURE AREA IS FORECAST TO DEVELOP IN THE PLAINS
AND MOVE TOWARD THE MIDWEST BY LATE WEDNESDAY OR THURSDAY.
SCATTERED THUNDERSTORMS...SOME OF WHICH MAY BE STRONG TO LOCALLY
SEVERE...COULD DEVELOP IN CENTRAL ILLINOIS THURSDAY.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT ANTICIPATED THROUGH TONIGHT.

$$

SMITH

[CrazyC83]

That seems correct.

Looking at models, this could be a one-two-three-four punch:

1) The warm front near the low center. That has been notorious for surprise tornadoes recently (such as on January 7 in Wisconsin) and that could be an issue in northern Iowa, Minnesota and western Wisconsin.

2) The dryline. Models seem to bring up 60-65 dewpoints into Nebraska and even South Dakota, and with CAPE now showing up to 1,500 j/kg2, that is certainly enough to trigger a major outbreak.

3) The cold front - round one. This has question marks, since it could squall out quickly. But depending on how fast it moves, it might remain supercellular across Iowa, Missouri and Arkansas.

4) The cold front - round two. Another tricky one, since moisture return doesn't appear to be that great on Thursday. However, a situation similar to November 15, 2005 is possible if moisture return increases (dewpoints are expected to be about 5 degrees lower all around at this point,). If round one busts, this may be more active than anticipated across the Midwest into the Mid-South.

[CrazyC83]

Excellent site with impressive data here: http://www.twisterdata.com/

While it only shows up to 84 hours (Wednesday evening), it shows some impressive data:

EHI - peak around 3.5
Helicity - peak around 600
CAPE - peak over 1,500
LI - around -5

For comparison, those values in the tornado impact areas during other recent cool-season outbreaks:

November 12/05 - November 15/05 - November 14/06 - March 1/07 - January 7/08 - February 5/08 - February 17/08

EHI: 2.0 - 5.0 - 3.5 - 5.0 - 3.5 - 5.0 - 2.5
Helicity: 400 - 700 - 700 - 800 - 600 - 1,000 - 500
CAPE: 750 - 1,500 - 750 - 1,500 - 1,000 - 1,250 - 1,000
LI: (-5) - (-4) - (-5) - (-7) - (-5) - (-6) - (-4)

[Shockwave]

Thanks Crazy83C for that info. The Feb. 5th , 2008 day is one I would like to forget. That whole day was errie. I do hope we see some action here in TN, not sure if we will though if those models keep trending northward.

[Weatherfreak14]

It looks right now, that the main threat will be from OK all the way to TN... And IN looks like they may get some severe weather also, most of my reletives live in Evansville and went through the Nov 05 tornado.

[CrazyC83]

Thanks Crazy83C for that info. The Feb. 5th , 2008 day is one I would like to forget. That whole day was errie. I do hope we see some action here in TN, not sure if we will though if those models keep trending northward.

The models haven't really been trending anywhere the last day, just intensifying the activity.

I'm having a hard time finding an analog since I can't recall ever a tornado outbreak so far north and west so late in the year.

Removing one of the two question marks and clarifying since it seems somewhat more likely now.

[CrazyC83]

00Z run:

EHI - peaking around 3.5 (maybe 4.0 locally)
Helicity - near 550 (up to 950 to the west, if that can line up with the severe weather - yikes!!!)
CAPE - approaching 2,000 J/kg2 in the central area
LI - around -7 to -8 over south-central Kansas
Dewpoints - Low to mid-60s in Kansas and Oklahoma, high 50s elsewhere
Temps - Mostly low to mid-70s except near 80 in southern areas (70s as far north as Lake Superior!)

Not pretty. It's the most ominous run yet. I'm guessing a 30%-hatched for the Day 3 outlook by the SPC. Outside chance at a Day 3 moderate risk.

[CKB 38]

im really excited to see how this all plays out!!! by the way im new to this forum...i live in peoria illinios...and i LOVE severe weather!!!

what do u think the chances of us seein some pretty decent severe weather in central illinois r for like wed night maybe...

[CrazyC83]

im really excited to see how this all plays out!!! by the way im new to this forum...i live in peoria illinios...and i LOVE severe weather!!!

what do u think the chances of us seein some pretty decent severe weather in central illinois r for like wed night maybe...

Probably not much until early Thursday with the squall line. Thursday afternoon MAYBE another round, but that would need greater moisture return (models are showing not too much then).